I can't understand why pkgsrc include meta-pkg depend everywhere, I
mean I
wanted to install only some kdebase stuff and it depend on
everything meta-

pkgs/kde4.

Same for k3b, konversation, kmess, why these pkg needs a full kde
installation
? Do you think konversation need kdeedu, kdegames, kdemultimedia ? I
don't

think so and pkgsrc is the only one framework including a full kde
installation I seen.

I suspect that in principle, you're right; in practice, though, it's
pretty hard.

I maintain a few packages. Figuring out the minimal set of
dependencies is difficult, since few software writers document it very
well. Even when they try, they often forget to list things that are
standard on their favorite Linux distribution. Let's face it, linux
is the native environment for much of pkgsrc; we're often in the
position of providing a similar-enough environment for most of it to
work.

Suppose I'm trying to create a package for something that's native to
the kde4 world. I could try to build the absolute minimum set of
prerequisites, but that's often an iterative process, and kde4 builds
take a *long* time. So I build some possible predecessors and try to
build my package. If it fails, I should delete the kde4 piece I just
tried -- and what it installed as its prerequisites -- and try again
with a different predecessor. Worse yet, there are often interactions
-- see pkg/33652 for one case where I had problems as a user of pkgsrc
-- and those, too, are hard on the maintainer. (That's probably not
the best example, but it was a very easy one for me to find.)

So what should people do when building packages? We all have limited
time and day jobs. Sometimes, one just has to make a very pragmatic
decision: assume that most of the users will need enough of the
components of the metapackage that it isn't worth trying to break it
apart. List everything as a prerequisite; it minimizes pain not only
for the maintainer, but also for users who will have fewer strange
interactions to cope with.